Ideally, this CRT-ness could be a Compiz plug-in. Let's say you could CRT-ize a window by pressing Meta-C or something like it.

Then just open a terminal full-screen, apply the plug-in and enjoy your vintage computer.

For best effect, change your font to a VT-100-like one (I prefer the 3278-like one, but that's a taste thing).

BTW, how hard is it to write a Compiz plug-in?